[mrtg] Re: Interpreting the graphs...recommendations

[Hunt, Chris]

Gabriel,

I understand that you are trying to efficiently use the bandwidth and think
that's great use of this tool....

However, 3300 is a 24 port system if I recall correctly, so if you use one
uplink you're talking about up to 24 * 100 users sharing the port. You need
to review the number of MAC address entries that the switch can store
against each port, as exceeding that will result in the switch operating
inefficiently - it achieves it's switching function by relying on the
contents of the tables which say which ports have which devices connected...


My knowledge is a little limited here, but if the switch cannot find a MAC
address on one port, it might try sending on all ports??? I'm sure that
someone will correct me if I'm wrong?

Although, you might find that an "uplink port" whatever the 3300 provides
has a larger MAC table memory. you could use MRTG to look at switch memory
usage if there's a supported mib?

Regards,
Chris Hunt,
Lehman Brothers.


-----Original Message-----
From: Gabriel David Custer [mailto:CUSTERG at cedarville.edu]
Sent: 05 November 2001 17:58
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Interpreting the graphs...recommendations



I've been running MRTG on a few of my 3Com 3300s for several weeks
now, and I'm trying use some of the information to decide if I should
try to make changes.  We arbitrarily set up a figure of having no more
than 100 nodes running on 100mbps switched copper ports per 100mb
fiber uplink.  I'm trying to determine if that is a reasonable guess. 
The MRTG graph indicates one of the 100 node uplinks averaging around
1.6% with maximimums (seldom) up to 20% of the fiber link.  For anyone
else use similar equipment for their edge switches, do you have a
standard number of nodes per uplink, or do you have a set percentage
of utilization you watch for prior to adding another uplink?  I can
add more 100mb fiber uplinks, but gigabit is currently cost
prohibitive due to excessive distance.

Thank you for your help...
Gabe Custer
Cedarville University

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